Camaena obtecta (H. Fischer, 1898)
Baudinella occidentalis F. Köhler, 2011
Mouldingia occidentalis G.A. Solem, 1984
Nipponochloritis occidentalis M. Azuma, 1982
Camaena ochthoplax (W.H. Benson, 1860)
Sphaerospira oconnellensis J.C. Cox, 1871
Ningbingia octava G.A. Solem, 1981
Papuina odilia W.S.S. Van Benthem-Jutting,1965
Papuanella ogeramuensis (W. Kobelt, 1914)
Satsuma okiensis H.A. Pilsbry & Y. Hirase,1908
Basedowena olgana G.A. Solem, 1993
Pleuroxia oligopleura R. Tate, 1894
Pleuroxia oligopleura numba T. Iredale, 1939
Ganesella omeiensis H.A. Pilsbry & T.C. Yen
Satsuma omoro H. Minato, 1982
Satsuma omphalodes H.A. Pilsbry, 1901
Landouria omphalostoma B. Páll-Gergely& A. Hunyadi, 2013
Camaena onae Thach, 2016
Ganesella onestera (J.F. Mabille, 1887)
Turgenitubulus opiranus G.A. Solem, 1981
Ganesella optima H.A. Pilsbry, 1902
Labyrinthus oreas F.C.L. Koch, 1844
Nanotrachia orientalis (G.A. Solem, 1984)
Westraltrachia oscarensis (J.C. Cox, 1892)
Nipponochloritis oscitans (E.C. Von Martens, 1881)
Nipponochloritis oscitans kiyosumiensis M. Azuma, 1982
Satsuma oshimae H.A. Pilsbry, 1901
Amplirhagada osmondi G.A. Solem, 1988
Nipponochloritis osumiensis (H.A. Pilsbry & Y. Hirase,1904)
Labyrinthus otis (J. Lightfoot, 1786)
Labyrinthus otis orthorinus H.A. Pilsbry, 1899
Pleuroxia overlanderensis G.A. Solem, 1997
Ganesella oxytropis (O.F. von Möllendorff,1901)
Camaena pachychila (E.A. Smith, 1893)
Xanthomelon pachystylum (L. Pfeiffer, 1845)